In the past, projectors have been configured so that the focus movement, the zoom movement, and the shift movement of a lens unit can be achieved by controlling drive motors, and in such a case, the function capable of adjusting the lens positions of the lens unit by controlling the respective drive motors has been provided.
As a device of controlling the drive motor described above, in the past, for example, there has been disclosed a technology of providing a feedback processing section for measuring the position of the actuator and feeding back the shift from the target position to the drive section to thereby make the drive section correct the shift, and a feedforward processing section for previously calculating the drive force to be input based on the target position of the actuator, then calculating the pattern of the drive force to be applied using the drive force thus calculated and a feedforward arithmetic expression set previously, and then transmitting the pattern of the drive force to the drive section, thereby making it possible to arbitrarily set the feedforward arithmetic expression in accordance with the distance from and the direction of the given target position using the feedforward processing section (see, e.g., Japanese Patent Publication No. 2001-100801).
Further, as another technology, there has been disclosed a technology of providing a control parameter correction section for a feedforward control device and a control parameter correction section for a feedback control device, and performing the latter correction using knowledge processing, thereby accurately optimizing the control parameters of the feedforward/feedback control devices (see, e.g., Japanese Patent Publication No. 6-102905). Further, as another technology, there has been disclosed a technology of determining whether the timing of the output of the feedforward control system and the output of the feedback control system are alternately by switching, or used together based on the fuzzy inference section (see, e.g., Japanese Patent Publication No. 6-202709).
However, since in the technologies described in the respective documents, the feedback control and the feedforward control are used together, the control requires a huge amount of calculation, and the cost of the processor or the like increases. Further, the feedback control can perform accurate position control, but has a problem that it takes time until reaching the target position. Therefore, if it is arranged that the position control is performed by the feedforward control, it is possible to control the time required for reaching the target position to be shorter, but there arises the problem of inferior accuracy of the position control.